A large number of organic compounds that can be potentially toxic are used extensively in a wide variety of materials or products. Representative examples of such materials include particle board, plywood, furniture, cabinets, and textiles containing a synthetic resin adhesive such as formaldehyde or a derivative thereof; urea formaldehyde foam insulation; paper products impregnated with wet strength agents; resins, adhesives, paints, varnishes, and the like, containing aliphatic and aromatic hydrocarbons, alcohols, ketones, and esters as vehicles, thinners, or solvents. These organic compounds fulfill a need, and therefore usage is expansive and commonplace. However, many such organic compounds used in the manufacture of these materials are volatile and emit antigenic or noxious fumes. Numerous precautions or safety standards have been implemented by industry to identify the sources of the volatile fumes, to control the exposure of the worker to these fumes, and to prevent the ingestion or inhalation of these fumes by the worker. However, it is not uncommon that after the installation of these materials or products in the house, office, or work area, volatile or gaseous organics continue to be emitted or released from the materials or products to the atmosphere of such an enclosed environment, which even occurs with materials bearing a surface treatment. Many of these gasses have known toxic characteristics, and can cause irritation to the skin, eyes, nose or throat, or cause headaches, drowsiness or digestive disorders. Although the problem is most severe with newly manufactured materials or products, the problem may be latent, and this noxious effect can be long-term and persist for several years after the manufacture and installation of the material.
This latent problem and lingering noxious effect exists, for example, in the case of formaldehyde typically used as an adhesive or as a resin component in wood products, and is known to manifest itself for as long as seven years following manufacture and installation. Formaldehyde is one of the world's most important industrial chemicals having a reported annual production of about 12 million metric tons. Wood products account for a large percentage of the total formaldehyde demand, and consequently these health and environmental problems with indoor air have become particularly aggravated. In fact, it is reported that most people in the industrialized nations spend up to about 90 percent of their time indoors, and therefore it is essential to provide a safe environment for the occupants. A number of U.S. governmental agencies have issued or are proposing to issue regulations limiting permissible amounts of formaldehyde emissions from various products and materials. For example, Department of Housing and Urban Development (HUD) has implemented such standards for particle board and plywood, as found in 24 CFR 3280.308 et seq. According to these standards, product certification is required by testing in a large scale test chamber, which may be augmented by more frequent small scale testing to monitor during production. The small scale testing, e.g., the two hour desiccator test, utilizes small samples cut from a large scale production line panel or board. The samples are first preconditioned by sealing the edges with paraffin, and then placed in a desiccator for vapor phase extraction of formaldehyde gas into distilled water. The solution is then analyzed by wet chemistry to determine the gaseous emissions. Additionally, the Science Advisory Board has assisted the Occupational and Safety Health Administration in providing standards for noxious emissions, including standard for formaldehyde emissions (see 29 CFR 1910, Occupational Exposure to Formaldehyde).
Other analytical devices have been developed for the purpose of detecting and monitoring gaseous or volatile toxins existing in an indoor environment, but these devices either require wet chemical analysis, such as the two hour desiccator test described above, or are limited to monitoring ambient or atmospheric air. For example, aqueous and solid media have been used for collecting formaldehyde from air samples, as reported by Matthews et al., "Solid Sorbent for Formaldehyde Monitoring", Analytical Chemistry, Vol. 54, No. 9, pp 1495-1498, August 1982, which utilizes 13X molecular sieve as a sorbent media; and by Liparl et al., "2,4-Dinitrophenylhydrazine-Coated Florisil Sampling Cartridges for the Determination of Formaldehyde in Air", Environ. Sci. Technol., Vol. 19, No. 1, pp 70-74, 1985, which utilizes Florisil (magnesium silicate) coated with 2,4-DNPH. Most of the techniques of this type, however, monitor ambient air only, and cannot be used for detecting a gaseous emission from a particular building material or product. However, the monitoring method of Matthews et al. has been used for determining gas emitted from a solid material, but this method and other similar methods require additional steps involving wet analysis to complete the sampling, in that the reaction product is eluted from the sorbent media and then analyzed by chromatography or spectrophotometry.
Thus, these techniques monitor the formaldehyde after it has escaped from the source and blended with the surrounding air, and therefore do not identify the source of the emissions; or, in the case of Matthews et al., cited above, for monitoring emissions from a solid material, the formaldehyde is first collected as emitted from the source, the formaldehyde eluted from the sorbent, and then in a separate step analyzed by wet chemistry.
A more simple technique utilizing a colorimetric detector for detecting formaldehyde in air is disclosed in U.S. Pat. No. 4,511,658 to Lambert et al. According to this patent, an inert support, such as filter paper or a granular absorbent, is coated with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, a ketone such as acetone, and a metal bicarbonate such as sodium bicarbonate. Formaldehyde in the air sample enters into the reaction chain, and in the presence of moisture (i.e., water), produces the chromophore having a purple color. Although the detector is simple and requires visual observation only for a color change, the device is limited to detecting formaldehyde in ambient or atmospheric air, and, most significantly, requires the presence of water as an exogenous reagent.
Tests strips comprising an inert substrate or carrier, such as paper or film, and impregnated with testing reagents that produce a visible color change are well known in the art. Soviet Union Patent 0728083, Apr. 15, 1980, discloses a strip indicator for determining acetone in air using moist tape impregnated with hydroxylamine hydrochloride and Bromophenol Blue, and assessed by photocolorimetry. Additional art disclosing detectors of this type include U.S. Pat. No. 3,443,903 to Heidelberg et al.; 4,427,632 to Okaniwa et al.; 3,043,669 to Charles; 4,558,012 to Nygen et al.; and 4,592,893 to Poppe. All of the disclosures in this group of U.S. patents relate to test strips for detecting a liquid analyte, particularly for use in testing body fluids such as blood serum or urine.
A test strip used for titrametric analysis is disclosed in U.S. Pat. No. 3,510,263 to Hach. According to Hach, the test strip, comprising a bibulous member such as filter paper, is impregnated with a titrant and indicator. The strip is immersed into the liquid sample. A change in indicator color will occur until the end point is reached, and because the test strip is provided with a printed calibration scale for the titrant, the concentration of the test solution can be read off the printed scale. Here again, the analyte is a liquid, and the test strip is immersed into the liquid sample.
A test strip of bibulous material such as filter paper is also disclosed in U.S. Pat. No. 3,409,405 to Mohan et al. The test strip, which is used for detecting formaldehyde in body fluids, is impregnated with phenylhydrazine hydrochloride, ferric ammonium citrate, and tribasic potassium phosphate. In use, the test strip is contacted with a sample of the body fluid and with hydrochloric acid, and the presence of formaldehyde is indicated by a visible color change. Here too, the test strip is useful for liquids only, and moreover requires an exogenous reagent, i.e., hydrochloric acid, as did the above patent to Lambert et al. requiring water.
A test method utilizing a carrier with a color-change indicator for detecting a volatile substance in a liquid is disclosed in U.S. Pat. No. 4,201,548 to Tomaoku et al. In this patent, the detector comprises a composite having a cover plate provided with sample holes or wells, and a gas permeable membrane covering one surface of the plate. A carrier impregnated with a chromogenic agent is contacted with the membrane, and a second cover plate, having either observing windows or being of a transparent material, is positioned on the opposite side of the carrier. A test sample of liquid is poured into the holes, and a vaporizing agent is added to the liquid. A volatilized component of the liquid is released and permeates the membrane, and upon contact with the chromogenic reagent, produces a color change. The test apparatus is described as useful for testing liquids such as blood, urine or waste water, and for determining the presence of ammonia, amines, halogens, nitrogen oxides, and sulfur compounds. The apparatus, however, is limited to testing small liquid samples, and requires the use of an exogenous reagent, i.e., vaporizing agent.
This invention has, therefore, as its purpose to provide an analytical device, and method of using same, for detecting in situ a gaseous or volatile analyte emitted from a solid material, thereby being source specific; further requires minimal or no technical training, instrumentation, operator time, special analyses; and is convenient, transportable, rugged, and inexpensive.